Textile-elastomer composite preferable for transfer or film coating and method of making said composite

ABSTRACT

The present, invention relates to a process for producing a fabric-elastomer composite that, when transfer or film coated, is preferable for use as an artificial leather substrate. The inventive procedure involves (a) producing an elastomer composition of at least four ingredients (an anionically-stabilized waterborne polymer dispersion, an acid-generating chemical, a cloud-point surfactant, and a foam-stabilizing surfactant); (b) incorporating sufficient gas into the liquid mixture to generate a spreadable foam; (c) applying the foam onto a porous textile substrate; (d) heating said foamed fabric until the elastomer coagulates over the fabric substrate; and (e) drying the resultant composite without destroying the coagulated structure. The resultant composite obtains a suppleness that is similar to that of leather and a surface that is suitable for transfer coating to produce artificial leather. The composite may be utilized as upholstery fabric in furniture or in automobiles, apparel, and the like. The particular composites produced are also contemplated within this invention.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.09/602,122, filed on Jun. 23, 2000 now U.S. Pat. No. 6,475,562, ofKirkland W. Vogt and Howell B. Eleazer for A FABRIC/ELASTOMER COMPOSITEPREFERABLE FOR TRANSFER-COATING AND METHOD OF MAKING SAID COMPOSITE.

TECHNICAL FIELD

The present invention relates to a process for producing a textilematerial that, when transfer or film coated, is preferable for use as anartificial leather substrate. The inventive procedure involves (a)producing an elastomer composition of at least four ingredients (awaterborne anionically-stabilized polymer dispersion, an acid-generatingchemical, a cloud-point surfactant, and a foam-stabilizing surfactant);(b) incorporating sufficient gas into the liquid mixture to generate afoam; (c) applying the foamed elastomer composition onto a poroustextile substrate; (d) heating the treated textile until the elastomercoagulates over the textile substrate; and (e) drying the resultantcomposite without destroying the coagulated structure. The resultantcomposite, herein disclosed, exhibits a suppleness that is similar tothat of leather and a surface that is suitable for transfer orfilm-coating to produce artificial leather. The four-ingredientpre-mixture is a long-lasting, shelf-stable composition which will notreact until it is exposed to sufficient amounts of heat, thus providingan improvement over the prior art. The particular compositions producedare also contemplated within this invention.

DISCUSSION OF THE PRIOR ART

Polymer latexes (e.g., polyurethane and acrylate) have been utilized ina variety of ways, most notably as coatings or finishes on fabricsurfaces. Such latexes may provide, for example, a barrier topotentially adverse environmental conditions. Furthermore, leathersubstitutes have also been produced through the use of waterbornepolymer latexes. Such substitutes provide an alternative to moreexpensive, genuine leather articles. Such artificial leather substratesmust exhibit the suppleness and appearance that are characteristic ofgenuine leather, and must withstand heavy and repeated use withinautomobile and furniture upholstery, for example.

Previous polyurethane-based leather substitute products includecomposites produced through the reaction of a polyurethane latex and anacid-generating chemical (specifically, hydrofluorosilicic salts). Sucha composition is disclosed in U.S. Pat. No. 4,332,710, to McCartney,entirely incorporated herein by reference. McCartney teachesheat-activated coagulation of a polyurethane latex in conjunction withonly an acid-generating chemical, such as salts of hydrofluorosilicicacid. Such a composition and method present some difficulties, primarilyin the use of an acid-generating chemical alone to provide ioniccoagulation. This two-component system often results in a non-uniformdistribution in the textile substrate and can form stringy structures,which are unattractive as suede leather substitutes. Of particularconcern are the environmental and safety issues associated with the useof hydrofluorosilicic acid salts, which are highly discouraged withinthe industry but which are patentee's preferred acid-generatingchemicals.

Other prior teachings involving polymer latex heat-activated coagulationinclude U.S. Pat. No. 4,886,702 to Spek et al. The '702 patent disclosesa method utilizing a composition comprising a waterborne polymer latex(including polyurethane and acrylate), a cloud-point surfactantcoagulant, and a blowing agent, which evolves gas during heating.However, such a composition does not produce preferable leather-liketextile products due to the stiff hand that results from the effect ofthe blowing agent. Second, the preferred blowing agent is freon, whichis being phased out of production due to its deleterious environmentalimpact. Third, the coagulation process requires the addition of acidand/or salt compounds, which have the potential to coagulate the latexmixture prior to contact with a textile substrate, thus resulting in anon-uniform dispersion on the substrate surface. Last, the shelf-life ofpatentees' composition is, at a maximum, only eight hours in duration,thereby placing certain limitations on manufacturing flexibility.

Furthermore, U.S. Pat. No. 4,171,391, to Parker, teaches polyurethanelatex coagulation within an aqueous ionic or acid bath. Because thedetermining factors are the type and amount of ionic material (or acid)and the rate of diffusion of such a constituent from the bath to thesubstrate material, such a procedure is difficult to control. As aresult, there is a lack of consistent uniform dispersion and coagulationfrom one textile substrate to another. Particularly with heavier fabricsubstrates, the necessary contact times may be as long as 30 minutes,translating into high costs for the manufacturer and, ultimately, theconsumer.

These shortcomings indicate a need, then, within the industry, forimproved leather-like textile-elastomer composites, which are relativelyinexpensive to make, which have a more realistic appearance and improvedaesthetic qualities when transfer or film coated, and which have anoverall better performance over the prior art.

SUMMARY

This invention concerns a leather-like textile-elastomer composite, anda method of producing this composite, the method comprising thesequential steps of:

(a) providing a textile fabric;

(b) producing a liquid elastomer composition comprising:

(i) a waterborne, anionically-stabilized polymer latex;

(ii) an acid-generating chemical;

(iii) a cloud-point surfactant; and

(iv) a foam-stabilizing surfactant,

wherein sufficient gas is incorporated into the liquid elastomercomposition to produce a foamed elastomer composition;

(c) applying the foamed elastomer composition of (b) to the textilefabric of (a);

(d) heating the coated textile to an initial temperature to effectuate auniform dispersion and cause coagulation of said elastomer compositionover the textile fabric; and

(e) subsequently heating the coagulated fabric to a temperature higherthan the temperature utilized in step (d) in order to dry, but notdestroy, the coagulated elastomer over the fabric.

Also, the invention concerns the elastomer composition of step (b) ofthe inventive method itself.

It is thus an object of the invention to provide an improved, moreaesthetically pleasing leather-like fabric-elastomer composite. The termfabric-elastomer composite refers to an article comprised of a textilefabric, which has been coated on at least one side with an elastomercomposition. An object of the invention is to provide a composite thathas a more realistic, leather-like appearance and is more aestheticallypleasing when transfer or film-coated. A further object of the inventionis to provide a relatively inexpensive method of making such acomposite, by providing an elastomer latex with a shelf-life of at leasttwo weeks and by providing an application method that allows greatermanufacturing control. Another object of the invention is to provide amethod of producing a leather-like article which includesenvironmentally safe, nontoxic, low odor, noncombustible chemicals. Yetanother object of this invention is to provide leather-like composites,which when transfer or film-coated, are suitable for all intended usesin which a user requires or desires a faux-leather substrate.

Nowhere within the prior art has such a specific heat-activatedcoagulating method utilizing a foamed elastomer composition comprising awaterborne, anionically-stabilized latex, an acid-generating compound, acloud-point surfactant, and a foam-stabilizing surfactant beendisclosed, practiced, or fairly suggested. Such an elastomer compositionprovides a significant advantage over the two-component (latex andacid-generator) and different three component (latex, cloud-pointsurfactant, and blowing agent) compositions of the prior art. Forinstance, the inventive composition has a shelf-life measured in weeks(at least two weeks of stability and non-coagulation after initialadmixing) instead of hours at a temperature as high as about 38° C.(100° F.). The coagulation occurs only after exposure to a heat sourceof sufficient temperature to effectuate such reactivity (such astemperatures greater than about 80° C. or 176° F.).

Additionally, the utilization of foaming to apply the inventive latexcoating facilitates production through the ability to control moreeffectively the amount of coating applied, the depth of penetration ofthe coating into the fabric, and the rate and uniformity of thecoagulation process. The prior art's teachings do not permit such anextensive and beneficial ability to manipulate the amount of penetrationand the location of the coating while controlling the coagulationreaction. In particular, the inventive method and composition provide ahigh level of coagulant uniformity within single composite substratesand also allow uniformity of appearance and performance between manydifferent composites at the large-scale manufacturing level.

Yet another improvement available with the inventive method andcomposition is the use of a strictly aqueous system rather than anorganic solvent-based system. Avoidance of organic materials providesless volatility, odor, combustibility, and toxicity as well asincreasing the heat stability of the final product. Of particularbenefit is the ability to utilize the inventive aqueous composition inconjunction with other compatible aqueous chemical systems used in otherareas of textile manufacturing. Such adaptability and compatibility withother textile manufacturing procedures and materials is very important,for example, in reducing the chances of toxic emissions during textileprocessing.

Finally, and perhaps most importantly, the inventive method andcomposition impart a soft, fine-structured coagulum leather-like finishto fabrics which is comparable to, if not better than, leather-likefinishes produced with organic solvent-borne systems (such as thosedescribed in U.S. Pat. No. 4,886,702, noted above). Thus, the inventivemethod and composition provide the means to produce, in a very safemanner, a fabric-elastomer composite having a desirable suppleness andappearance, which, when transfer or film-coated, effectively simulates agenuine leather article.

The term fabric-elastomer composite refers to an article comprised of atextile fabric, which has been coated on at least one side with anelastomer composition. As noted above, the inventive foamed elastomercomposition comprises five materials: a waterborne polyurethane latex,an acid-generating chemical, a cloud-point surfactant, afoam-stabilizing surfactant, and sufficient gas that, when incorporated,produces the foamed product.

An anionically-stabilized polymer latex is an emulsion or dispersionformed from a polymer, an anionic surfactant, and water. Polyurethane,acrylic, or polyurethane-acrylic latex is preferable, but any waterborneanionically-stabilized polymer latex may be used. The preferred latexesare those having at least a 30% solids content, with greater than 50%solids being more preferred. One preferred example of ananionically-stabilized polyurethane latex is EX-62-655 (40% solids),available from Stahl. A suitable anionically-stabilizedpolyurethane-acrylic latex is Paranol T-6330 (50% solids), availablefrom Parachem. Examples of suitable anionic surfactants for use in thepolymer dispersion include, but are not limited to, poly-acrylic acidcopolymers, sodium laurel sulfate, aryl and alkyl benzene sulfonatelike, but not limited to, the proprietary Rhodacal DS-10 (from Rhodia).In addition to the anionic surfactant and water, a nonionic surfactantmay also be included in the polymer dispersion. Examples of a nonionicsurfactant include polyvinyl alcohol and ethoxylated surfactants, suchas Pluronic F-68 (from BASF). Also well known in the art is theincorporation of carboxyl or sulfate groups into the backbone of thepolymer in order to help stabilize the latex. The waterborne criterionis of utmost importance within this invention primarily to insure thatpotentially environmentally harmful organic solvents are not presentwithin the elastomer composition.

The term acid-generating compound denotes a chemical which is not anacid at room temperature, but which produces an acid upon exposure to aheat source. Examples include, but are not limited to, ammonium acidsalts like ammonium sulfate, ammonium phosphate, and organic acidesters. One particularly suitable class of compounds that both meet thisdescription and that provide superior results with little or no harmfulenvironmental impact are organic acid esters. Some specific types ofthese compounds include ethylene glycol diacetate, ethylene glycolformate, diethylene glycol formate, triethyl citrate, monostearylcitrate, a proprietary organic acid ester available from High PointChemical Corporation under the tradename Hipochem AG-45, and the like.The most preferred compound is ethylene glycol diacetate, available fromApplied Textile Technologies under the tradename APTEX™ Donor H-plus.

The term cloud-point surfactant is intended to encompass anysurface-active agent that becomes less water soluble upon exposure tohigher temperatures. This type of surfactant easily binds with thepolymer latex upon gelling and facilitates the uniform coagulation ofthe latex over the entire contacted textile substrate. Specificsurfactants that meet such requirements include poly(ethylene) oxides,poly(ethylene/propylene) oxides, polythio ethers, polyacetals,polyvinylalkyl ethers, organo-polysiloxanes, polyalkoxylated amines, orany derivatives of these listed compounds, with the preferred beingpolyalkoxylated amines, available from Clariant under the tradenameCartafix U™.

The term foam-stabilizing surfactant includes any surface-active agentthat improves the ability of the inventive composition to entrain, andretain, air. Particular examples include, but are not limited to, alkylbenzene sulfates and sulfonates (Rexoprene series from Emkay Chemical)like sodium laurel sulfate (also sold under the name Stephanol AM fromStepan Corporation), sodium dioctyl sulfosuccinate, dodecyl benzenesulfonate, alkyl amine oxides (Unifroth series from Unichem Corp.),alkyl phosphates (Synfac series from Milliken Chemical), ammoniumstearate (Henkel), water-soluble cellulose derivatives (Hercules Inc.),and Alkasurf DAP-9 (Rhodia). In the absence of a foam-stabilizingsurfactant, gas could be introduced into the elastomer composition, butthe gas would not be incorporated or retained.

The proportions required within the inventive elastomer composition arebased upon the ratio of weights between the latex and each of theremaining components. For instance, ratios between the latex and each ofthe other components (namely, the acid-generating compound, thecloud-point surfactant, and the foam-stabilizing surfactant) should bein the range of 5:1 to 200:1, with preferred ranges of from about 10:1to about 50:1. The Examples below further illustrate the utilization ofsuch ranges of weight ratios.

The gas associated with the foam production is selected from the groupconsisting of atmospheric air, mixtures of oxygen, nitrogen, andhydrogen, and the like. Atmospheric air is preferred as an inexpensiveand readily available source. The gas is incorporated at a pressure inthe range of 1 pound per square inch (gauge) to 100 pounds per squareinch (gauge), with a preferred range of about 25 p.s.i.g. to about 50p.s.i.g. The acceptable weight ratio of air to latex within thecomposition is in the range of 0.1:1 to 50:1, with a preferred range of3:1 to 8:1.

The air, or other gas, is incorporated into the foam by mechanicalagitation. The air-incorporation process, commonly called foaming, maybe accomplished through any accepted procedure. Examples, not intendedas limitations, include whipping with a Hobart mixer or a Gaston Systemsmechanical foamer. The foamed elastomer composition can then be appliedwith screen coating, knife coating, parabolic foam coating, and thelike, without any limitation intended.

It has been found that incorporating air into (or foaming) the inventivecomposition offers several benefits over conventional applicationmethods. First, the amount of elastomer applied to the textile substrateis less than the amount that would be used in a dip application, thusresulting in cost savings to manufacture. Secondly, because theincorporated air reduces the density of the inventive composition, thesubstrates that are produced following coagulation have aestheticproperties that more closely resemble leather. In addition, the airincorporated into the foam increases the volume of the coating,improving application and creating an improved surface for transfercoating. Finally, the manufacturer has greater control over theapplication of the elastomer. As a result, the foam mixture does nothave to be applied to both sides of the fabric, as it would be with adip application. Further, the degree of penetration of the foam into thetextile substrate can also be controlled.

Subsequently, the elastomer-coated textile fabric is heated. Thisheating step generates an acid and gels the cloud-point surfactant,which then uniformly coagulates the inventive latex over the entiresubstrate. The temperature required to initiate the reaction depends onthe particular acid-generating compound utilized. However, in general,the requisite temperature should be at least 80° C., with a hightemperature being about 130° C.

The boiling point of water is the preferred temperature, particularlywhere a steam application (and most preferably a saturated steamapplication of 100° C. to 110° C.) is used. Such conditions arepreferred because moist heat (steam) provides the most effectiveexposure for the elastomer composition. The presence of moisture permitsa greater level of control over the reaction since the addition of dryheat generally vaporizes the aqueous portion of the inventive latex,which promotes the undesirable formation of a continuous polymer film.The latex must remain moist in order for proper and uniform coagulationto ensue. Therefore, the elastomer composition preferably must containwater during the entire reaction. An exposure time of from about 1minute to about 10 minutes, in a steam application, may be used. Thepreferred exposure time is about 2 minutes in a steam application. Theutilization of a steam heating step again provides a distinct advantageover the prior art by retaining strictly aqueous solvent reactionconditions.

Alternatively, the coated fabric may also be exposed to rapid heating bya microwave or radio frequency heat source, which does not provide anappreciable loss of moisture to the overall elastomer composition. Anexposure time of from about 1 second to about 1 minute in a microwaveapplication may be used.

Yet another alternative is to expose the coated fabric to heating by aconvection heat source. Preferably, the temperature should be raisedslowly to allow the coating to coagulate prior to dry and prevent thecoating from cracking. An exposure time of from about 10 seconds toabout 10 minutes in a convection oven may be used.

After the first heating step, the composite is dried, preferably by highconvection, low temperature heating (preferably, but not limited to,less than 130° C.) or by microwave or radio frequency heating in orderto prevent continuous film formation on the fabric surface. The secondheating step is engineered to dry the composite without destroying thecoagulation of the elastomer composition.

The textile fabric utilized within the inventive process may compriseany synthetic or natural fiber or blend of such fibers. As merelyexamples, and not intended as limitations, the textile fabric may beconstructed from fibers of polyester, nylon (-6 or -6,6), cotton,polyester/cotton blends, wool, ramie, spandex, and the like. The fabriccan have a knit, woven, or non-woven construction. The preferred knitsubstrate is made of polyester, and most preferably polyethyleneterephthalate yarns. The preferred woven substrate is made of cotton.

The textile fabric may be treated with dyes, colorants, pigments,ultraviolet absorbers, softening agents, soil redisposition agents,lubricating agents, antioxidants, flame retardants, rheology agents, andthe like, either before foaming or after, but with a preference for suchadditions before foaming. Within the elastomer composition, there may beincorporated any of the above-listed textile additives, as well aslubricating agents or cross-linking agents. One particularly desiredagent is a softening/soil redisposition/lubricating additive LubrilQCX™, available from Rhône-Poulenc. Desirable pigments include PP14-912and PP14-905 available from Stahl.

It is believed that sanding or napping the fabric prior to theapplication of the elastomeric composition will improve the hand of thefabric-elastomer composite and will improve the adhesion between thefabric and the composition. The sanding or napping process has beenfound to impart, in the fabric-elastomer composite, a suede-like feel onthe effective back of the composite. It is believed that sanding ispreferable for knit fabrics and that napping is preferable for wovenfabrics.

In addition, in some circumstances, it may be desirable to subject thefinished fabric to a calendering process. Calendering improves theadhesion characteristics of the final product (that is, thefabric-elastomer composite that has also been transfer coated). Inaddition, the calendering process produces a feel similar to that ofsuede on the effective back of the transfer-coated fabric-elastomercomposite. Calendering can be achieved on any equipment designed forsuch purpose, including, but not limited to, a Briem calender having aheated drum width of approximately 20 inches. Because the settings fortemperatures, pressures, and speeds are all related to one another, arange of appropriate settings could be used to achieve the desiredeffect. For example, one such preferred setting involves a temperatureof 150° F., a pressure of 40 kg/cm², and a speed of 2 yards/minute.

After calendering, the fabric-elastomer composite is subjected to eithertransfer or film coating to create a three-layer composite structurethat resembles genuine leather in both appearance and tactilecharacteristics. In both transfer and film coating, the additionalcoating is applied in contact with the elastomer coating. The technicalface of the textile becomes the effective back of the three-layercomposite. The transfer coating process involves the application of aplurality of individual layers of polyurethane (typically, at least two,but up to five or more) to a paper backing. The coatings are thenadhered to the fabric-elastomer composite, and the paper backing isremoved, resulting in a three-layer leather-like product. The filmcoating process involves adhering a sheet-like film substrate to thefabric-elastomer composite, typically using adhesives and heat tolaminate the film to the composite. The term “film” is used to mean anythin, flexible, sheet-like substrate, comprising a metallic substrate, aplastic or polymeric film, or a felt-like or flocked textile substrate.

The inventive composite may be utilized as upholstery fabric forfurniture or in automobiles; within garments or apparel; or for anyother purpose in which a textile leather substitute is desired.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the inventive method and composition areset forth in the following Examples.

EXAMPLE 1

A mixture of 100 grams of EX-62-655 (Stahl), 10 grams of APTEX™ DonorH-Plus (Applied Textile Technologies), 10 grams of Cartafix U™(Clariant), 0.5 grams of Alkasurf DAP-9 (Rhodia), 4 grams Unifroth 0529(Unichem, Inc.), and 15 grams of Lubril QCX™ (Rhône-Poulenc), wereblended together. The latex was whipped in a Hobart mixer on high forthree minutes. A second mixture was made as before but 3.8 grams ofStephanol AM and 3.9 grams of 33% ammonium stearate (Henkel) wassubstituted for the Unifroth 0529. Again the latex was whipped in aHobart mixer on high for three minutes. Table 1 shows that the densitiesof the two resulting foams were approximately equivalent.

TABLE 1 I.D. Foam-stabilizing surfactant Foam Density Foam 1 4 gUnifroth 0529 0.24 g/cc Foam 2 3.8 g Stepanol AM and 3.9 g 33% ammonium0.25 g/cc stearate

EXAMPLE 2

A 9 ounce/square yard tricot knit polyester fabric with 85% 100/100textured filament yarn as the face yarn and 15% 20/1 monofilament as theground yarn was used as the textile substrate. The fabric was dyed,brushed, dried, and sanded on both sides. A mixture of 100 grams ofEX-62-655 (Stahl), 1.5 grams of APTEX™ Donor H-Plus (Applied TextileTechnologies), 1.5 grams of Hipochem AG-45 (High Point Chemicals), 3grams of Cartafix U™ (Clariant), 0.5 grams of Alkasurf DAP-9 (Rhodia),3.89 grams of 33% ammonium stearate (Henkel), 3.81 grams of Stephanol AM(Stepan), 15 grams of Lubril QCX™ (Rhône-Poulenc), and 0.2 grams ofPP14-905 pigment (Stahl) were blended together. The latex was whipped ina Hobart mixer on high for three minutes. The fabric was wet with waterand nipped at 40 psi between rollers. The air-incorporated latex foamwas spread on the fabric and knife-coated with an 80 mil gap. The fabricwas placed in a convection oven at 250° F. (121° C.) for 8 minutes,where the coating coagulated and dried. The resulting textile compositefelt like leather and produced excellent synthetic leather whentransfer-coated.

EXAMPLE 3

An 8.5 ounce/square yard woven cotton fabric with 57 ends/inch and 68picks/inch was used as the textile substrate. The fabric was denselynapped on the sateen face and was scratch-napped on the back. A mixtureof 69.2 grams of Paranol T-6330 (Parachem), 6.9 grams of APTEX™ DonorH-Plus (Applied Textile Technologies), 6.9 grams of Cartafix U™(Clariant), 0.3 grams of Alkasurf DAP-9 (Rhodia), 2.8 grams of 33%ammonium stearate (Henkel), 2.2 grams of Stephanol AM (Stepan), 10.4grams of Lubril QCX™ (Rhône Poulenc), and 0.2 grams of PP14-912 pigment(Stahl) were blended together. The latex was foamed with a mechanicalfoamer (Gaston Systems) using an air-to-latex ratio of 5:1. The foamedlatex was knife coated on the fabric with a Mascoe knife coater andcoagulated and dried in a tenter-oven at 225° F. for 1.0 minutes and at250° F. for 0.7 minutes. The resulting textile composite felt likeleather and produced excellent synthetic leather when transfer-coated.

What is claimed is:
 1. An elastomer composition comprising: (i) awaterborne, anionically-stabilized polymer latex; (ii) anacid-generating chemical; (iii) at least one cloud-point surfactant; and(iv) at least one foam-stabilizing surfactant; and (v) sufficient gas toproduce a foam when incorporated into said elastomer composition.
 2. Theelastomer composition of claim 1 wherein (ii) is ethylene glycoldiacetate.
 3. The elastomer composition of claim 1 comprising: (i) awaterborne, anionically-stabilized polymer latex; (ii) anacid-generating chemical; (iii) at least one cloud-point surfactant;(iv) at least one foam-stabilizing surfactant; and (v) sufficient gas toproduce a foam when incorporated into said elastomer composition;wherein the weight ratio of (i) to (ii) is from about 5:1 to about200:1; the weight ratio of (i) to (iii) is from about 5:1 to about200:1; the weight ratio of (i) to (iv) is from about 5:1 to about 200:1;and the weight ratio of (i) to (v) is from about 0.1:1 to about 50:1. 4.The composition of claim 3 wherein the weight ratio of (i) to (ii) isfrom about 10:1 to about 50:1; the weight ratio of (i) to (iii) is fromabout 10:1 to about 50:1; the weight ratio of (i) to (iv) is from about10:1 to about 50:1; and the weight ratio of (i) to (v) is from about 3:1to about 8:1.